Do you need a statement of purpose if it's not mentioned?

[chron]

I am specifically looking at Canadian schools, so maybe this is a difference between what US schools usually want vs. Canada. I keep hearing about this statement of purpose I'm supposed to write, but at least some of the schools I'm looking at don't seem to mention it. In some cases, they mention a statement of research interests which lists what areas you want to study and potential supervisors. Sometimes it says they just want that for the PhD not Master's (I am applying for a Master's). Sometimes there's no mention of a statement or even any additional documentation at all, which makes it unclear if even a resume/CV is required. Sometimes it says they want a statement of intent, but the description seems to suggest it's mostly about what you want to study or future goals, whereas the sample statements of purpose I've seen on the web are mostly about describing your past and elaborating on your resume.

 

What should I be submitting to them?